Copper base alloy

ABSTRACT

Copper base alloys containing essentially, by weight, 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, balance substantially all copper. Continuously cast castings of the alloy are preferred. The alloys, after cold working, exhibit retention of high strength characteristics including high tensile strengths after exposure to high annealing temperatures for substantial periods. The alloys also have high electrical and thermal conductivity before and after exposure to high annealing temperatures for substantial periods as well as satisfactory elongation.

United States Patent [1 1 Kranz et al.

[73] Assignee: American Smelting and Refining Company, New York, N.Y.

[22] Filed: Nov. 4, 1971 [21] Appl. No.: 195,776

[52] U.S. Cl. 75/153 [51] Int. Cl. C22c 9/00 [58] Field of Search 75/153; 148/32 [56] References Cited UNITED STATES PATENTS 3,700,842 10/1972 Attia 75/153 X 2,027,807 1/1936 Burghofi'... 75/160 2,102,742 12/1937 Poland 75/153 2,264,287 12/1941 Betterton et al. 75/153 X 2,268,938 1/1942 Hensel 75/153 2,268,939 1/1942 Hensel... 75/153 2,268,940 1/1942 Hensel 75/153 1 1 Nov. 20, 1973 FOREIGN PATENTS OR APPLICATIONS 1,706 3/1957 Japan 75/153 18,063 9/1963 Japan 75/153 OTHER PUBLICATIONS Metal Industry, Sept. 10, 1943, pages 170, 171 & 172

Primary Examiner-Charles N. Lovell Att0rneyElw00d J. Schaffer et al.

[57] ABSTRACT Copper base alloys containing essentially, by weight, 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, balance substantially all copper. Continuously cast castings of the alloy are preferred. The

2 Claims, 4 Drawing Figures Patented Nov; 20, 1973 2 She aim-Shut 1 FIG FIG

Patented Nov. 20, 1973 2 Shoots-Shut 2 FIG.

FIG

COPPER BASE ALLOY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a copper base alloy and more particularly to copper base alloys which, when cold worked, are characterized by retention of high tensile and yield strengths after exposure to elevated annealing temperatures for appreciable periods. Additionally this invention relates to the preparation of such alloys.

2. Description of the Prior ART Copper based alloys containing 0.25 to 5 percent cadmium, 0.05 to 3 percent tellurium, balance copper are disclosed in U. S. Pat No. 2,268,938. U.S. Pat. No. 2,268,939 refers to binary copper base alloys containing 0.05 to 3 percent tellurium, balance copper. An alloy containing 1 percent copper, 78 percent silver, 0.6 percent tellurium, 13 percent selenium and 7.4 percent sulphur is disclosed in U.S. pat. No. 2,397,756. U.S. Pat. No. 2,847,303 shows copper base alloys containing about 0.01 percent to 1 percent zirconium. 0.005 to 0.5 percent phosphorous, balance copper; U.S. Pat. No. 3,370,942 discloses copper base alloys containing between 1 percent and 20 percent of tellurium oxide; and U.S. Pat. No. 2,239,179 discloses alloys containing 01-33 percent tellurium, 0.1 -l chromium, balance copper.

A copper base alloy containing 16 oz. per ton of silver as well as 0.009 percent phosphorous and 0.12 percent tellurium has been reported in the prior art. However such alloy is prohibitively expensive or economically disadvantageous for use as automotive radiator fin stock and as electrical connectors due to the presence of the large amount, viz. 16 oz. per ton, of the expensive silver.

The requirements for commercially acceptable copper base alloys for rolling into sheet for use in the automotive radiator industry in accordance with the International Copper Research Association (also known as INCRA) is that the alloy when rolled into sheet have (I) a minimum tensile strength of 48,000 pounds per square inch after annealing at 710F. for 3 minutes, (2) a minimum elongation of 0.5 percent after the heat treatment of (l), and (3) an electrical conductivity above 90 percent I.A.C.S. (I.A.C.S. being an abbreviation of the International Annealed Copper Standard).

SUMMARY OF THE INVENTION In accordance with the present invention, copper base alloys are provided which, after cold working, exhibit retention of high strength characteristics including acceptable, high tensile strengths in accordance with INCRA for the automotive radiator industry, after exposure of the alloys to elevated temperatures, for instance high temperatures of annealing, for a substantial period. The alloy contains essentially, by weight, 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, remainder substantially all copper. The alloys of this invention also meet the requirements of commercially acceptable copper base alloys for rolling into sheet for the automotive radiator industry in accordance with INCRA for conductivity and elongation as previously set forth herein, inasmuch as the alloys herein have elongations considerably in excess of the 0.5 percent minimum and conductivities materially greater than 90 percent I.A.C.S.. Further the alloys of this invention are economical to produce compared with the prohibitively expensive silver-containing alloys, and are commercially feasible for the automotive radiator and also the electrical connector industries.

The tellurium is critical in the alloys herein for attaining the retention of the high tensile strength after exposure of the cold worked alloy to high annealing temperatures for appreciable periods. The 0.02 percent by weight lower limit of the telluriumis of critical importance for the reason that with amounts of tellurium below 0.02 percent Te, the retention of acceptable, high tensile strength of the alloy with exposure to high annealing temperatures is not attained. The 0.04 percent by weight upper limit of the tellurium is also of importance for the reasons that substantially maximum retention of high yield strength of the alloys on exposure to high annealing temperatures is attained at 0.04 percent tellurium, with little or no improvement in such strength retention properties with amounts of tellurium in excess of 0.04 percent by weight, and the use of the expensive tellurium in the alloys in amounts appreciably above 0.04 percent by weight tending to be disadvantageous from an economic standpoint. It is critical to avoid an amount of phosphorous appreciably in excess of 0.0 1 5 percent in the alloys herein as the electrical conductivity of the alloy is lowered materially with an amount of phosphorous above 0.015 percent. The phosphorous raises the recrystallization temperature of the alloys of this invention, and the phosphorous also supplements the recrystallization temperature raising capability imparted by the copper telluride (Cu Te). With amounts of phosphorous appreciably below 0.002 percent, such desirable results due to the presence of the phosphorous may not be attained.

In another embodiment of this invention, the alloys contain a small amount of oxygen as an additional constituent for improving the electrical conductivity of the alloy. Specifically, in this embodiment, the alloys contain oxygen as an additional constituent in amount from a trace amount up to 0.05 percent by weight inclusive. More specifically these alloys usually contain the oxygen in amount, by weight of 0.0002 percent to 0.05 percent inclusive. The oxygen can be introduced or incorporated into the alloys herein by any suitable means or method. As exemplary, the oxygen can be introduced or incorporated in the alloys herein as oxygen present in scrap copper, for example the oxygen present in No. 1 scrap or in scrap wire bars, or the oxygen can be introduced into the alloys being held in the ladle or holding furnace from the atmosphere or during pouring of the molten metal through air, such as during pouring from the ladle or holding furnace.

The copper base alloys of the present invention are prepared by melting copper in a suitable melting or holding furnace or vessel to form a pool of molten copper, adding phosphorous, preferably as a phosphorous master alloy, to the molten copper pool and adding tellurium to the molten pool. The phosphorous and tellurium are added to the molten pool essentially in proportions such as to provide a molten metal pool containing essentially, by weight, 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, remainder copper. The thus-obtained molten metal is then introduced into a mold of the desired shape, and a solidified copper base alloy casting subsequently withdrawn from the mold. In the alloys of the embodiment containing the oxygen up to 0.05 percent by weight as an additional ingredient, the oxygen is introduced or supplied into the alloy by the means or method previously disclosed herein.

The copper-phosphorous-tellurium alloys of the pres ent invention free of or containing oxygen in amount up to 0.05 percent inclusive can be cast into castings of any desired shape or configuration and of any desired dimensions, and the casting carried out by any desired casting method. Thus the casting can be by continuous casting which includes semi-continuous casting within its scope, or by static or non-continuous casting in suitable molds. Continuous casting can be utilized to produce cakes of the instant alloy, billets of the alloy, or other desired shapes of the alloy. The static or noncontinuous casting can be utilized to produce wire bars on the conventional wire bar casting wheel or ingots in stationary molds. Continuous casting of the alloys to produce cakes can be effected utilizing the continuous casting apparatus including the block graphite mold disclosed and claimed in U.S. Pat. No. 2,946,100 to R. Baier et al. and assigned to the common assignee.

In continuous or semi-continuous casting of the copper-phosphorous-tellurium alloys of this invention to produce cake utilizing the continuous casting apparatus including the block graphite mold disclosed and claimed in U.S. Pat. No. 2,946,100, a pool of the molten alloy containing essentially, by weight, 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, remainder copper is established in a suitable holding furnace, ladle or other suitable vessel. The molten alloy is fed continuously into one end of the mold provided with cooling means for cooling and hence solidfying the alloy, usually a water-cooled graphite mold. The alloy cools and solidifies as its passes through the mold, and is withdrawn from the other end of the mold as a continuous casting in the form ofa cake. The withdrawn or emerging cake is lowered into a cooling well by means of a hydraulic lowering mechanism as more molten alloy is poured on top of the congealed alloy in the mold and solidifies. After the casting of the cake is completed, the cake is lifted from the well by a crane, and, if required, sawed to the lengths specified by the customer. These cakes, prior to sawing, may typically have length of 12 inches to 25 feet, width of 25 inches to 36 inches and height of about inch. The mold is ordinarily reciprocated lengthwise of the casting during the casting operation.

In continuous or semi-continuous casting of the copper-phosphorous-tellurium alloys of this invention to produce billets, the molten alloy is supplied or fed from a pool of such molten alloy in a suitable holding furnace or other suitable vessel into one end of an open-ended mold provided with a cooling section, and a continuous casting withdrawn from the other end of the mold. The mold is surrounded by a waterjacket and water or other coolant is circulated through the jacket. In starting the casting operation, a conventional starting bar or rod is inserted into the mold while the mold is empty of molten alloy after which molten alloy is supplied into the mold, the withdrawal rolls are started which withdraws the casting from the mold, and circulation of coolant through the jacket is begun. After the continuous casting passes below the withdrawal rolls, it may be severed into billets of any desired length by a saw. A suitable mold and apparatus for the continuous casting of the alloys of this invention to produce billets is disclosed in U.S. Pat. No. 3,089,209 to R. Baier et al.

and assigned to the common assignee. The billets may have dimensions of length of 10 inches to 72 inches and diameter of 3 inches to 12 inches.

In static or non-continuous casting of the alloys of this invention to produce wire bars, the molten alloy herein is fed into the usual wire bar molds wherein it cools and solidifies. The solidified wire bar castings are then removed from the molds. The alloys of this invention may also be cast by static or non-continuous casting to form ingots or ingot bars, if desired.

The cold working of the alloys of this invention can be, for example, rolling of the alloy to, for example, sheet form; drawing of the alloy to, for example, wire; and forging of the alloys to form, for example, electrical fittings.

The following test samples or examples and test data further illustrate the invention:

Continuous cast castings and static or noncontinuously cast castings of alloys of the present invention and of copper per se and of a copperphosphorous alloy were cast. The continuous cast castings were cast from an induction heated graphite crucible. This system is inherently reducing and a slight positive pressure of nitrogen was maintained over the melt. The continuous cast castings were 34: inch diameter rod weight 10 pounds. Casting rates in the continuous casting averaged 7 inch minute, utilizing a 0.1 second on 0.2 second off cycle at a running speed of 21 inch/minute. The temperature of the melt for the continuous casting was maintained at about 2,150F.

In preparing the static cast castings, 8-to-10 pound charges of copper were induction melted in graphite crucibles. Alloys additions were calculated and preweighed so that from each melt four or five compositions could be obtained. For each composition two %inch diameter by 6 inch long slugs were poured through air into preheated graphite book molds. Alloy additions for the next desired composition were then immersed in the melt. Alloy Test Samples Nos. 1-5 of Tables I and II which follow were produced in this manner.

In the fabrication and preparation of test samples, five inch lengths of the three-fourth inch continuously cast rod were heated at 850C. for one-half hour in a muffle furnace and then hot rolled to three-eighths inch square in cross section. The rods were then reheated 20 minutes at 850C. and quenched. The thus hot-rolled rods were cold rolled to 0.030 inch thickness, which was a cold reduction of about 92 percent.

Strips for tensile and yield strength testing were prepared by cutting 5 inch lengths, which were reduced in width at the center by grinding and smoothing with emery paper. The samples were heat treated in a salt bath for 3 minutes at 710F. and quenched.

Wires for electrical conductivity testing were drawn from the rolled rods of three-eighths inch square cross section to standard 0.081 inch diameter wires. The w re we e nnea ed. 2.0 m ut s. aL 9Q? In preparing the various alloy compositions of the test samples of Table I and II hereinafter set forth, the P was added as a master alloy of composition 14.7 percent P-balance Cu in the form of shot, and the Te as a master alloy of composition 7.85 percent Te-balance Cu in the form of waffle, percentages being by weight. The four day cathode copper and wire bar copper utilized in preparing the various alloy compositions of the test samples of Table l hereinafter set forth was of the following compositions:

Wirebar parts per million 4-Day Cathode parts per million The actual chemical composition of the copp'efliase alloy compositions of the test samples prepared as disclosed supra are set forth in Table I which follows. In Table I CC and SC under the columnar heading Casting Method" means continuous casting and static casting respectively.

TABLE I COMPOSITIONS OF ALLOYS Test Cu Casting P Te sample no. source Method l 4 day cathode SC .013 Z 4 day cathode SC .0072 .0l2 3 4 day cathode .0062 .009 .0l4 4 4 day cathode SC .0069 .026 .009 5 4 day cathode SC .0065 .041 .013 6 Wire Bar CC .014 .038 .0036 7 Wire Bar CC .0088 .040 .0002

fine particles, which are dispersed throughout the tinuous copper matrix. The copper telluride particles are believed to impede recrystallization and accompanying softening when the alloy is exposed to elevated temperature of annealing. Thus the in situ precipitate of Cu Te in the alloys of this invention is believed to explain the excellent strength retention of the alloys after their exposure to the high temperatures for appreciable periods of time.

In the Drawings FIG. 1 is a photomicrograph of an as cast copper base alloy also containing phsophorous and tellurium of the invention;

FIG. 2 is a photomicrograph of a copper base alloy also containing phsophorous and tellurium of the present inventior as cold rolled; V v V FIG. 3 is a photomicrograph of a copper base alloy also containing phosphorous and tellurium of the present invention after cold rolling and then annealing for 200 minutes at 7l0F.; and I W V W V I FIG. 4 is a photomicrograph of a copper base alloy also containing phosphorous and tellurium of the present invention after cold rolling and the annealing for 330 minutes at 7l0F.

The alloy composition of FIGs 1-4 inclusive was, by weight, 0.0088 percent phosphorous, 0.04 percent tellurium, 0.0002 percent oxygen, remainder copper. Referring to FIG. 1, the fine or small diameter dark dots are believed to be copper telluride particles dispersed in the continuous copper matrix. The dark lines in FIG. 1 are the grain boundaries. The alloy in FIG. 1 is shown at 400X magnification and has been continuously cast as a rod. In FIG. 2, the continuously cast alloy rod has been hot rolled and then cold rolled to a 92 percent reduction, and the alloy is shown at 400X magnification.

TABLE IL-MECHANICAL AND PHYSICAL PROPERTIES BEFORE AND AFTER HEAT TREATMENT Tensile strength Yield strength (lbs. per square inch) (lbs. per square inch) Elongation, percent Electrical conductivity After After After percent Test Sample N 0. As rolled annealing As rolled annealing As rolled annealing A 0.8.

1 (C 1) 59, 800 33, 800 59, 400 4 27 101- 75 2 (Cu, .0072% P) 59, 500 34, 000 2 34 101. 75 3 (Cu, .0062% P, 009% Te).. 59, 400 24,100 2 22 101.85

0,400 4 (Cu, .0069% P, .026% Te)... 60,200 53,400 2 9 100.35

51,900 8 5 (Cu, .0065% P, 041% Te) 60,700 33 888 60, 600 gfi'ggg 2 2 101.35 6 (Cu, 014% P, 036% Te) 60,800 383 59,600 5 g 93.2

' 56, 000 54, 700 6 7 (Cu, .0088% P, 040% Te)--. 64, 800 56, 600 64, 500 54,700 1 6 94.1

The test data of Table II shows that alloy Test Samples Nos. 4, S, 6, and 7, which were alloys in accordance with this invention, retained tensile strengths in excess of 48,000 pounds per square inch and indeed in excess of 50,000 pounds per square inch after exposure to a temperature of7l0F. for 3 minutes, and in this respect were a considerable improvement over Test Samples Nos. l, 2 and 3 not of this invention. The test data of Table II also shows that alloy Test Samples Nos. 4, 5, 6, and 7 of this invention retained acceptable elongations and I.A.C.S. electrical conductivities after their exposure to the 7lOF. annealing temperature.

Retention of cold worked properties of the alloys of this invention after exposure of the alloys to elevated temperatures such as, for instance, the high annealing temperatures appears to occur due to the presence of the precipitate of tellurium as copper telluride (Cu Te) The characteristic laminar form grains due to the rolling are shown in FIG. 2. The final or small diameter dark dots in FIG. 2 are copper telluride particles. With reference to FIG. 3, incipient recrystallization is shown with the tensile and yield strengths of the alloy decreas- DESCRIPTION OF THE PREFERRED EM ODIM NTS- The phosphorous is preferably contained in the copper base alloys of this invention in the amount, by

weight, of 0.005 to 0.015 percent phosphorous.

An especially preferred alloy of this invention contains essentially, by weight, 0.01 percent phosphorous. 0.04 percent tellurium, remainder substantially all copper.

The copper base alloys of the present invention are preferably continuously cast as contrasted with static or non-continuous casting to form castings, for the rea sons the continuous cast castings have surfaces free or substantially free of defects and scuffs, whereas the undesirable surface defects and surface scuffs not infrequently are present in the castings cast by static or noncontinuous casting. Further, a quick chill of the molten alloy is achieved in the continuous casting which considerably lessens or eliminates the tendency for segregation to occur in the alloy. However, such quick chilling of the molten alloy is not attained in the static or non-continuous casting of the alloy. Continuous casting of the alloys of this invention to form cake, billets, rods, tubes or any other desired shape casting can be effected and is within the spirit and scope of this invention. However, the continuous casting (also referred to as semi-continuous casting) of the alloys herein to produce cakes is most preferred. The cake is capable of being readily rolled into sheet which is suitable for forming auto radiator fi n stock and electrical connectors.

In the method for the preparation of the copper base alloys herein, although the phosphorous master alloy and tellurium may be added simultaneously to the mo]- ten copper pool, preferably the phosphorous master alloy is added to the molten copper pool prior to the addition of the tellurium.

The phosphorous master alloy is a master alloy of phosphorous and copper, for example such a master alloy containing, by weight, percent phosphorous, remainder copper and in the form of shot.

The tellurium is preferably added to the molten metal pool as a master alloy such as a master alloy of tellurium and copper. Exemplary of such tellurium master alloy is a master alloy containing, by weight, 45-50 percent tellurium, remainder copper. Less preferably the tellurium can be added to the molten metal pool as elemental tellurium.

In additional tests carried out, an alloy of this invention containing, by weight, 0.01 percent phosphorous, 0.04 percent tellurium, balance copper was subjected to annealing at 710F. for an extended time. The alloy has been continuously cast into a rod and then cold rolled to form a sheet prior to the annealing heat treatment. The ultimate tensile strengths and yield strengths of the alloys at the heating times enumerated in Table III are set forth hereinafter in Table Ill.

TABLE III Extended Time Annealing Heat Treatment of Cu 0.1% P 195 c gy The test results of Table Ill shows that the Cu P Te alloy of this invention retained acceptable tensile strengths even after being subjected to 710F. for 200 minutes.

What is claimed is:

1. A continuously cast copper base alloy casting consisting essentially, by weight, of 0.002 to 0.015 percent phosphorous, 0.02 to 0.04 percent tellurium, 0.0002 percent to 0.05 percent oxygen, balance copper, said alloy having fine precipitate particles of copper telluride (Cu Te) dispersed throughout a continuous matrix of copper, the copper telluride particles impeding recrystallization and accompanying softening of the alloy when the alloy is exposed to elevated annealing temperature, the phosphorous supplementing a recrystallization temperature-raising capability imparted by the copper telluride, the oxygen resulting in an improved electrical conductivity of the alloy, said alloy when cold worked characterized by retention of high tensile and yield strengths after exposure to high annealing temperature for an appreciable period, said alloy meeting INCRA requirements for use in automotive radiators by having when rolled into sheet and after being annealed at 710 F. for 3 minutes a high tensile strength which meets the INCRA tensile strength requirement of a minimum 48,000 pounds per square inch, an elongation in excess of 0.5 percent, and a conductivity greater than percent I.A.C.S., the surfaces of said casting being substantially free of defects.

2. The continuously cast casting of claim 1 in the form of a cake.

P0- 0 ITED S'IATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,773,503 I Dated November 2L 1973 Inventor) Paul J. Kranz, Victor Little, Jr. and Michael Myers It is certifiedthat error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 12, "ART" should read --Art--; line 13,

- fi'based" should read --base--; line 20, "pat." should read --Pat.--.

Column 4, line 27, "weight" should read "Weighing"; .line 34, "Alloys" should read --Alloy--; line 59, "Wires." should. read --wire. Column 5, line 10, "Tc" should read --Te--. Column 6,

I lines 12 and 15, "phsophorous" in each such line should read --phosphorous+- line 24, "the" should read --t hen--; line 54, "final" should read ---fine--.

Signed and sealed this 9th day or'Ju1 '197L.

(SEAL) Attest:

MCCOY M. GIBSON, JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents 

2. The continuously cast casting of claim 1 in the form of a cake. 